1. Field of the Invention
The present invention relates to a clutch connection control system for a motor-driven speed change apparatus in which gear shift and disconnection and connection of a clutch are performed by using an electric motor. In particular, the present invention relates to a clutch connection control system for variably controlling a connection speed of the clutch on the basis of turning speeds of a clutch drive side and a clutch driven side.
2. Description of Related Art
As opposed to a related speed change apparatus for carrying out gear shift by operating both a clutch pedal (or clutch lever) and a gear shift lever, a motor-driven speed change apparatus for electrically carrying out gear shift by using a motor has been known, for example, from Japanese Patent Laid-open No. Hei 1-122741.
To shorten the time required for clutch connection and improve riding comfort upon clutch connection, the above related art speed change apparatus is configured such that an operational speed of a clutch release mechanism, that is, a turning speed of a drive motor is controlled in such a manner that a turning speed difference between a clutch drive side and a clutch driven side follows a predetermined time function.
An earlier application (Japanese Patent Laid-open No. Hei 11-82709) filed by the present applicant has disclosed a technique in which a clutch release mechanism upon clutch connection is operated at a high speed until a predetermined timing estimated as a clutch connection point and is operated at a low speed after the predetermined timing.
With this configuration, since the clutch is moved at a high speed in an operational region in which a clutch drive side is not in contact with a clutch driven side and is moved at a low speed in an operational region in which the clutch drive side is connected to the clutch driven side, it is possible to shorten the time required for speed change and to improve riding comfort upon speed change.
According to the above-described first related art (Japanese Patent Laid-open No. Hei 1-122741), a turning speed difference between the clutch drive side and the clutch driven side is controlled to be reduced with an elapsed time as shown in FIG. 33 of the present invention. To be more specific, as the speed change control starts by turning the drive motor, the clutch drive side and the clutch driven side, the turning speeds of which are different from each other, begin to come into contact with each other (which is called a semi-clutch state). Since the semi-clutch state proceeds with an elapsed time, the turning speed difference also becomes gradually smaller, and when the clutch drive side and the clutch driven side are perfectly brought into contact with each other, the turning speed difference becomes zero, to thus end the speed change control.
The control method of the first related art, however, has a problem in that if the turning speed difference becomes larger again by the driver""s operation of an accelerator after start of the speed change control, for example, at a time to in FIG. 33, the clutch drive side is rapidly connected to the clutch driven side in order that the turning speed difference is immediately made to follow the time function as shown by a broken line in FIG. 33, with a result that riding comfort upon speed change is degraded.
The above-described second related art (Japanese Patent Laid-open No. Hei 11-82709) also has the following problem: namely, according to this technique, the operation for clutch connection is performed at a low speed after the predetermined timing estimated as the clutch connection point; however, if the connection point is predetermined in consideration of differences among respective clutch mechanisms and deterioration of each clutch mechanism with an elapsed time, it cannot be close to an actual clutch connection point. Therefore, the operational speed must be changed into the above low speed at such a predetermined point which is considerably far from the actual clutch connection point. Accordingly, a time consumed for driving the clutch at the low speed becomes longer. That is to say, it is difficult to significantly shorten the time required for clutch connection.
An object of the present invention is to solve the above-described technical problems of the related arts and to provide a clutch connection control system capable of shortening the time required for clutch connection, preventing the degradation of riding comfort upon clutch connection, and ensuring a good operability.
To achieve the above object, according to the present invention, there is provided a clutch connection control system comprising: clutch release means for disconnecting and connecting a clutch drive side from and to a clutch driven side by turning an electric motor; drive side turning speed detecting means for detecting a turning speed of the clutch drive side; driven side turning speed detecting means for detecting a turning speed of the clutch driven side; turning speed difference detecting means for detecting a difference between the detected turning speed of the clutch drive side and the detected turning speed of the clutch driven side; and control means for controlling a disconnecting and connecting speed of the clutch, which is disconnected and connected by the clutch release means, on the basis of the detected turning speed difference; wherein the control system further includes rate-of-change detecting means for detecting a time-dependent rate of change of the detected turning speed difference; and the control means carries out clutch connection at a first speed until the time-dependent rate of change of the detected turning speed difference becomes a specific value or less, and the control means carries out clutch connection at a second speed lower than the first speed after the time-dependent rate of change of the detected turning speed difference becomes the specific value or less.
The time-dependent rate of change of a difference between the turning speeds of the clutch drive side and the clutch driven side represents a clutch connection state. Accordingly, a clutch connection start point can be accurately determined, on the basis of the time-dependent rate of change of the turning speed difference, irrespective of differences between respective clutch mechanisms and deterioration of each clutch mechanism with an elapsed time. Upon the connection of the clutches, with the configuration of the present invention, since the clutch drive side and the clutch driven side come close to each other at a high speed until the clutch connection start point determined as described above and come close to each other (come into contact with each other) at a low speed after the clutch connection start point, it is possible to shorten the time required for clutch connection, prevent the degradation of riding comfort, and ensure good operability.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.